1. Field of the Invention
The present invention relates to an image scanner and, in particular, to an image scanner which can directly scan a document and effectively obviate an optical error problem arising from a sheet of glass located between a document to be scanned and an image sensor in the prior art.
2. Description of the Prior Art
At present, almost all the structural designs of the existing image scanners apply the principles of a photocopy machine. That is, a glass plate is used as a platform for receiving an image document to be scanned. A light source of a bar type locates under the glass plate and moves from a first side to a second side thereof so that the light is emitted onto every part of the document. Then, a reflecting mechanism reflects the light which is reflected from the document to an image sensor of a CCD (Charge-Coupled Device) or CIS (Contact Image Sensor) type, which locates under the glass plate, so that the image data on the document can be scanned and obtained.
As the designs of the existing image scanners are almost all of the above type, the only aspect which can be changed is probably the choice of the image sensor. One of the most widely-used image sensors is the image sensor of a CIS type. Such a CIS image sensor utilizes densely-arranged light-guiding posts to directly transmit the light which represents a scanned image to the sensors for lowering the optical transmission toss, promoting the receiving quality and only utilizing light sources of lower intensity.
However, even when an image scanner adopts a CIS image sensor, the light transmission path for receiving a scanned image remains the same, that is, the light must pass through the glass plate to and from a document. The existence of the glass in the light transmission path will cause a degree of optical loss and error so that the quality of a scanned image is flawed. Therefore, there is a need to have an image scanner which can substantially obviate the above-described problems occurring in the prior art.